This application is the U.S. National Phase under 35 U.S.C. xc2xa7371 of International Application PCT/JP00/00508, filed Jan. 28, 2000, which claims priority based on JP 1999-37480, filed Feb. 16, 1999.
The present invention relates to a process for producing phosphorohalidate (halogenated phosphoric acid ester).
Phosphorohalidates are chemical substances which are useful in a wide variety of fields as raw materials or intermediates for pharmaceutical preparations, agricultural chemicals and the like or as resin additives such as flame retardants, plasticizers and the like or intermediates thereof. For such uses, the purity should be as high as possible.
Phosphorohalidates are usually obtained by reacting a phosphorus oxyhalide with an aromatic hydroxy compound. A Lewis acid catalyst is often used for the purpose of suppressing the generation of the by-product triaryl phosphate during the reaction and increasing the reaction rate.
However, in such a method of producing phosphorohalidates, the crude product obtained from the reaction usually contains not only its reaction products, i.e., phosphorodihalidate and phosphoromonohalidate, but also the Lewis acid catalyst, the by-product triaryl phosphate, and the starting materials, i.e., phosphorus oxyhalide and aromatic hydroxy compound. As a result, in order to produce high purity phosphorodihalidate suitable for use as a pharmaceutical raw material or intermediate or as a reaction retarding agent for molding sand, etc., the crude phosphorohalidates obtained from the reaction (crude reaction product) need to be purified by distillation and each component contained in the crude reaction product needs to be isolated. However, when a crude reaction product containing a Lewis acid catalyst is distilled, a disproportionation reaction occurs during the distillation process. Two molecules of phosphorodihalidate tend to convert into one molecule of phosphoromonohalidate and one molecule of phosphorus oxyhalide. Two molecules of phosphoromonohalidate tend to convert into one molecule of phosphate and one molecule of phosphorodihalidate. Therefore, the purity and yield of the desired phosphorohalidate can not be substantially increased even through purification by distillation.
A primary object of the invention is to solve the above problem and provide a process for producing high-purity phosphorohalidate in a higher yield using a Lewis acid catalyst. The process can produce phosphorohalidate containing no impurities such as the phosphorus oxihalidate and aromatic hydroxy compound used as starting materials and the catalyst.
The present inventors carried out intensive research to solve the problem and found the following: when a crude reaction product obtained by reacting a phosphorus oxyhalide with an aromatic hydroxy compound in the presence of a Lewis acid catalyst is purified by distillation in the presence of an alkali metal salt, the disproportionation reaction is suppressed and the desired phosphorohalidate can be obtained in high purity and high yield by an economical and simple distillation process. The present invention was accomplished based on the above finding.
Specifically, the present invention provides the following processes for producing phosphorohalidate and for purifying the same.
1. A process for producing phosphorohalidate, the process being characterized in that a crude reaction product obtained by reacting a phosphorus oxyhalide with an aromatic hydroxy compound in the presence of a Lewis acid catalyst is purified by distillation in the presence of an alkali metal salt.
2. The process for producing phosphorohalidate according to item 1 wherein the alkali metal salt is an alkali metal carbonate.
3. The process for producing phosphorohalidate according to item 1 or 2, wherein 0.25 to 10 moles of the alkali metal salt is used per mole of the Lewis acid catalyst.
4. The process for producing phosphorohalidate according to any one of items 1 to 3, wherein the distillation for purification is carried out at a temperature of 20 to 230xc2x0 C.
5. The process for producing phosphorohalidate according V to any one of items 1 to 4, wherein the phosphorohalidate is at least one member selected from the group consisting of diphenylphosphoromonochloridate and monophenylphosphorodichloridate.
6. A process for purifying phosphorohalidate, the process being characterized in that a mixture containing a phosphorodihalidate, a phosphoromonohalidate and a Lewis acid catalyst is purified by distillation in the presence of an alkali metal salt.
The process for producing phosphorohalidate according to the present invention is characterized in that the crude reaction product obtained by reacting a phosphorus oxyhalide with an aromatic hydroxy compound in the presence of a Lewis acid catalyst is purified by distillation in the presence of an alkali metal salt. In this description, this process is divided into two steps, i.e., a step for producing a crude reaction product from a phosphorus oxyhalide and an aromatic hydroxy compound (hereinafter referred to as xe2x80x9creaction stepxe2x80x9d) and a step for purifying the crude reaction product by distillation (hereinafter referred to as xe2x80x9cpurification stepxe2x80x9d), and is described below.
Reaction Step
In the reaction step, a phosphorus oxyhalide and an aromatic hydroxy compound are reacted in the presence of a Lewis acid catalyst.
Useful phosphorus oxyhalides include, for example, phosphorus oxychloride, phosphorous oxybromide and the like. Preferred is phosphorus oxychloride. The phosphorus oxyhalides can be used singly or in combinations of two or more.
Useful aromatic hydroxy compounds include, for example, compounds having an OH group directly bound to an aromatic ring such as a benzene ring, a naphthalene ring or an anthracene ring, i.e., aromatic compounds having a phenolic OH group. In addition, one to three substituents such as alkyl groups or halogen atoms may be bound to the aromatic ring. Two or more of the aromatic rings may be bound to each other with a single bond, an alkylene group, a sulfone group, etc. Alkyl groups useful as substituents on the aromatic rings include straight or branched chain alkyl groups having about 1 to 9 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, hexyl, heptyl, octyl, nonyl and the like. Useful halogen atoms include chlorine, bromine and the like.
Specific examples of aromatic hydroxy compounds include phenol, (o-, m- or p-)methylphenol, (o-, m- or p-)ethylphenol, (o-, m- or p-)n-propylphenol, (o-, m- or p-)isopropylphenol, (o-, m- or p-)n-butylphenol, (o-, m- or p-)sec-butylphenol, (o-, m- or p-)tert-butylphenol, (o-, m- or p-)isobutylphenol, (o-, m- or p-)tert-butyl-2-methylphenol, (o-, m- or p-)tert-butyl-4-methylphenol, (o-, m- or p-)pentylphenol, (o-, m- or p-)hexylphenol, (o-, m- or p-)heptylphenol, (o-, m- or p-)octylphenol, (o-, m- or p-)nonylphenol, (o-, m- or p-)chlorophenol, (o-, m- or p-)bromophenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)dimethylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)diethylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-n-propylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)diisopropylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-n-butylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-sec-butylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-tert-butylphenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)dichlorophenol, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)dibromophenol, (2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)trimethylphenol, (2,3,5- 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)triethylphenol, (2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)tripropylphenol, (2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)tri-tert-butylphenol, (2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)trichlorophenol, (2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)tribromophenol, hydroquinone, resorcin, catechol, bisphenol A, bisphenol S, bisphenol F, (1- or 2-)naphthol, (2,2xe2x80x2-, 4,4xe2x80x2-, 2,3-)biphenol, (1-, 2- or 9-)anthracenol and the like. Herein, xe2x80x9co-, m- or p-xe2x80x9d means that the benzene ring has a substituent at the ortho position, metha-position or para-position. xe2x80x9c2,3-, 2,4-, 2,5-, 3,4- or 3,5-xe2x80x9d means that the benzene ring has substituents at the 2,3-, 2,4-, 2,5-, 3,4- or 3,5-positions. xe2x80x9c2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-xe2x80x9d means that the benzene ring has substituents at the 2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-positions. The same shall be applied hereinafter.
These aromatic hydoxy compounds may be used singly or in combinations of two or more.
Among the aromatic hydoxy compounds, phenol, methylphenol, dimethylphenol and the like are preferred from the viewpoint of commercial availability. Particularly preferred is phenol.
The reaction is preferably carried out using about 0.25 to 4 moles of the aromatic hydroxy compound per mole of the phosphorus oxyhalide. A specific mixing ratio for the reaction may be selected according to the desired phosphorohalidate. For example, a reduced phosphorus oxyhalide/hydroxy compound molar ratio produces a larger proportion of diphenylphosphoromonohalidate. An increased phosphorus oxyhalide/hydroxy compound molar ratio produces a larger proportion of phenylphosphorodihalidate.
Usable Lewis acid catalysts include known ones. Specific examples are aluminum chloride, magnesium chloride, zinc chloride, ferric chloride, stannic chloride, titanium tetrachloride and the like. Especially preferred is anhydrous magnesium chloride. The Lewis acid catalysts may be used singly or in combinations of two or more.
Preferably, the Lewis acid catalyst is used in a proportion of about 0.01 to 2 parts by weight per 100 parts by weight of the phosphorus oxyhalide, more preferably about 0.1 to 1 parts by weight. An excess of the Lewis acid catalyst tends to increase the occurrence rate of side reaction, resulting in a lower yield. On the other hand, an insufficient amount of the catalyst tends to achieve insufficient catalytic effect.
The reaction between the phosphorus oxyhalide and the aromatic hydroxy compound, i.e., the esterification reaction, can be carried out at atmospheric pressure or under reduced pressure. Generally, the reaction is preferably carried out in the absence of water. The reaction is usually carried out at 20xc2x0 C. to 230xc2x0 C. A preferable range is between 50xc2x0 C. and 200xc2x0 C. A suitable reaction temperature may be selected according to the desired phosphorohalidate.
The reaction time varies depending on the amounts and kinds of starting materials used, reaction temperature, and the like. The reaction time may be suitably chosen to selectively and efficiently produce the desired phosphorohalidate.
The reaction may be carried out in the presence of an organic solvent, depending on the characteristics and reactivity of the starting materials and the phosphorohalidate to be obtained. Useful organic solvents include any organic solvents that can dissolve the starting materials and the reaction product, have a boiling point higher than the reaction temperature and are inert to the reaction. Examples of such organic solvents are benzene, toluene, xylene, isopropyl benzene, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, chloroform, tetrachloromethane, n-heptane, n-hexanes and the like. These solvents may be used in combinations of two or more. The amount of the organic solvent used should be approximately enough to fully dissolve the aromatic hydroxy compound. An excess of the solvent can prolong the reaction time or require a long time to recover the organic solvent after the reaction process, thus being undesirable. When a liquid starting material is used, the other starting materials may be dissolved therein and reacted.
The reaction product from the above reaction contains phosphorohalidates. Specific examples are phosphorohalidates represented by the formula (1) 
wherein R1 and R2 are the same or different and represent an aryl group; the aromatic ring of the aryl group may have at least one type of substituent selected from the group consisting of halogen atoms and alkyl groups; X is a halogen atom; and n is 0 or 1.
Specifically, in the formula (1), examples of the aryl groups include the same groups as the residues resulting from the removal of the OH group from the aromatic hydroxy compounds. Examples of the halogen atoms and the alkyl groups include the same as the halogen atoms and the alkyl groups which are substituents of the aromatic hydroxy compound.
Of the phosphorohalidates represented by formula (I), phosphorodihalidates wherein n=0 include, for example, phenyl phosphorodichloridate, (o-, m- or p-)chlorophenyl phosphorodichloridate, (o-, m- or p-)bromophenyl phosphorodichloridate, (o-, m- or p-)hydroxylphenyl phosphorodichloridate, (o-, m- or p-)methylphenyl phosphorodichloridate, (o-, m- or p-)ethylphenyl phosphorodichloridate, (o-, m- or p-)n-propylphenyl phosphorodichloridate, (o-, m- or p-)isopropylphenyl phosphorodichloridate, (o-, m- or p-)n-butylphenyl phosphorodichloridate, (o-, m- or p-)sec-butylphenyl phosphorodichloridate, (o-, m- or p-)tert-butylphenyl phosphorodichloridate, (o-, m- or p-)pentylphenyl phosphorodichloridate, (o-, m- or p-)hexylphenyl phosphorodichloridate, (o-, m- or p-)heptylphenyl phosphorodichloridate, (o-, m- or p-)octylphenyl phosphorodichloridate, (o-, m- or p-)nonylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)dichlorophenyl phosphorodichloridate, (2,3- 2,4-, 2,5- 2,6-, 3,4- or 3,5-) dibromophenyl phoophorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)dimethylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2, 6-, 3,4- or 3,5-)diethylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4-, or 3,5-)di-n-propylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)diisopropylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-n-butylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-sec-butylphenyl phosphorodichloridate, (2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-tert-butylphenyl phosphorodichloridate, (2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)trimethylphenyl phosphorodichloridate, (2,3,5- 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)triethylphenyl phosphorodichloridate, tris[(2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4, 5-)tripropylphenyl phosphorodichloridate and like aryl phosphorodihalidates.
Phosphoromonohalidates wherein n=1 include, for example, diphenyl phosphoromonochloridate, (o-, m- or p-)dichlorophenyl phosphoromonochloridate, (o-, m- or p-)dibromophenyl phosphoromonochloridate, (o-, m- or p-)dihydroxylphenyl phosphoromonochloridate, (o-, m- or p-)dimethylphenyl phosphoromonochloridate, (o-, m- or p-)diethylphenyl phosphoromonochloridate, (o-, m- or p-)di-n-propylphenyl phosphoromonochloridate, (o-, m- or p-)diisopropylphenyl phosphoromonochloridate, (o-, m- or p-)di-n-butylphenyl phosphoromonochloridate, (o-, m- or p-)di-sec-butylphenyl phosphoromonochloridate, (o-, m- or p-)di-tert-butylphenyl phosphoromonochloridate, (o-, m- or p-)dipentylphenyl phosphoromonochloridate, (o-, m- or p-)dihexylphenyl phosphoromonochloridate, (o-, m- or p-)diheptylphenyl phosphoromonochloridate, (o-, m- or p-)dioctylphenyl phosphoromonochloridate, (o-, m- or p-)dinonylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3, 4- or 3,5-)dichlorophenyl phosphoromonochloridate, bis-(2,3- 2,4-, 2,5- 2, 6-, 3,4- or 3,5-)dibromophenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)dimethylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3, 4-or 3,5-)diethylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3, 5-)di-n-propylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3, 4-or 3,5-)diisopropylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3, 5-)di-n-butylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2, 6-, 3,4- or 3,5-)di-sec-butylphenyl phosphoromonochloridate, bis-(2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)di-tert-butylphenyl phosphoromonochloridate, bis-(2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)trimethylphenyl phosphoromonochloridate, bis-(2,3,5- 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)triethylphenyl phosphoromonochloridate, bis-(2,3,5-, 2,4,5-, 2,3,6-, 2,3,4-, 2,4,6- or 3,4,5-)tripropylphenyl phosphoromonochloridate and like diaryl phosphoromonohalidates.
The crude product thus obtained from the reaction contains a phosphorodihalidate, a phosphoromonohalidate and the catalyst residue. Under certain reaction conditions, it may also contain unreacted starting materials, triaryl phosphate and the like.
Purification Step
In the purification step, the crude reaction product obtained from the reaction step is purified by distillation in the presence of an alkali metal salt.
The means of purification by distillation can be roughly classified into batch distillations and continuous distillations. These distillations are further divided into atmospheric distillations and reduced pressure distillations. Any of these distillation means can be used in the present invention. A specific distillation means can be selected according to the composition and amount of the crude reaction product to be treated and the like. Particularly preferred are distillations under reduced pressure because the crude reaction product is subjected to a lower amount of heat, resulting in suppression of the disproportionation reaction.
Using rectification equipment is an effective way to isolate a phosphorodihalidate or a phosphoromonohalidate as a single compound from phosphorohalidates.
With regard to the conditions for purification by distillation, the degree of vacuum, distillation temperature, distillation time and the like can be selected according to the types and amounts of phosphorohalidates and catalyst in the crude reaction product, etc.
For commercial scale manufacturing, the degree of vacuum is preferably in the range of about 0.5 to 300 mmHg.
The distillation temperature is preferably in the range of about 20xc2x0 C. to 230xc2x0 C. A distillation temperature higher than 230xc2x0 C. is undesirable because it tends to drastically accelerate the disproportionation reaction of phosphorohalidate. On the other hand, if the temperature is lower than 20xc2x0 C., a large amount of energy is required to cool the distillate with the condenser, thus being undesirable.
The alkali metal salt used in the distillation system is preferably in a proportion of about 0.25 to 10 moles per mole of the Lewis acid catalyst used in the reaction process, more preferably about 0.5 to 2 moles. If the amount of the alkali metal salt used is too small, it is not possible to sufficiently suppress disproportionation. On the other hand, an excess of the alkali metal salt does not further increase its effects, thus being uneconomical. Furthermore, an excess of the metal salt has the adverse effect of tending to decompose the desired product.
Examples of alkali metal salts include carbonates such as sodium carbonate, sodium hydrogencarbonate, potassium carbonate and potassium hydrogencarbonate; and chlorides such as sodium chloride and potassium chloride. Carbonates are preferred because even a small amount of carbonate can sufficiently suppress the disproportionation of phosphorohalidates. Particularly preferred is sodium carbonate. In this case, the alkali metal salt is solid and the crude reaction product is liquid. Therefore, it is preferable that the two components be in sufficient contact with each other, particularly preferably by stirring during distillation or fully stirring before distillation. A larger contact area between the alkali metal salt and the crude reaction product results in a greater disproportionation suppression effect. Therefore, fine powder of alkali metal salt is preferable to granular one.
In the case of using a solvent in the reaction process or reacting a hydroxy compound with an excess of phosphorus oxyhalide, it is preferable that the solvent, phosphorus oxyhalide and like low boiling point compounds and hydrogen chloride contained in the crude reaction product be removed by evaporation before the distillation process.
According to the above process of purification by distillation, phosphorodihalidate and phosphoromonohalidate can be separated from the crude reaction product and obtained with high purity in high yield. Phosphorodihalidate or phosphoromonohalidate can also be isolated as a single compound in high purity and high yield.
The purification step can be carried out subsequently to the reaction step in a process for producing phosphorohalidate. Alternatively, the purification step can be carried out as a purification method for a mixture containing phosphorodihalidate, phosphoromonohalidate and Lewis acid catalyst, independently from the reaction step. For example, after repeated production of the crude reaction product by reacting a phosphorus oxyhalide with an aromatic hydroxy compound, the crude product is transferred to a treatment vessel other than the reaction vessel. The distillation treatment is then carried out under the above conditions, whereby phosphorohalidates can be separated from a mixture of phosphorodihalidate, phosphoromonohalidate and Lewis acid catalyst and obtained with high purity in high yield. Such a process efficiently provides phosphorohalidates.
Known purification methods such as filtration and membrane separation can be used to purify the phosphorohalidates obtained by the process of the present invention, provided that the purification methods do not adversely affect the product.
The qualities such as purity, hue and metal content of the phosphorohalidates obtained by the process of the invention can be controlled to match needs by appropriately selecting the production conditions in the above production process and optionally further using one or more other known purification methods.
The production process of the present invention can suppress the disproportionation reaction more effectively than the conventional purification processes by distillation, resulting in reduction of by-products and achieving production of phosphorohalidates in high purity and high yield. This production process is especially advantageous for producing high-purity phosphorodihalidate or phosphoromonohalidate as a single compound.